Which is more secure and private than Signal or Briar?

Signal is recommended by Snowden and is safest now. On the other hand, an app called Briar is also attracting attention. Briar can be connected via Bluetooth without using Wifi and mobile lines.
Which is stronger in terms of security and privacy? Is Briar’s Bluetooth encrypted?

As mentioned in other threads started by you, no one can seriously talk about security of a product or service without a threat model.

Besides, Briar and Signal are developed for different use cases. Briar tries to be a resilient peer-to-peer messenger while Signal tries to be a solid crypto messenger. If you use both, you will immediately see that you can’t directly compare them since they come with different features (including different security features).

See also points mentioned by the EFF regarding “secure messenger”: https://infosec-handbook.eu/blog/discussion-secure/#sm

What do you mean here? Encryption of the Bluetooth connection? Look at the KNOB attack that was in the media recently.

Briar is more anonymous in the sense that you don’t need a phone number to use it. Signal is well known, well audited and very secure messaging service.

I think what you mean by “encrypted bluetooth” is are your communications encrypted when you message via bluetooth. Briar is end-to-end-encrypted so that means only you and the person you are messaging are able to decrypt communications. And yes, bluetooth is an encrypted hardware protocol (correct me if i’m wrong)

The current standard for key negotiation is very likely completely broken, see KNOB attack. The KNOB attack allows attackers to repeatedly downgrade the key size, so it becomes easily brute-forceable. Finally, an attacker can decrypt communcation between devices. Only Bluetooth Low Energy (Bluetooth LE) isn’t affected.

However, if applications encrypt their traffic on layers on top of Bluetooth, their communication isn’t affected by this. (And we still don’t know what @pinp meant.)

Normal Bluetooth LE prevents MITM attacks, which was completely different from the KNOB vulnerability found inside the actual devices.

http://www.fte.com/WebHelp/BPA600/Content/Documentation/WhitePapers/BTLE/HowEncryptionWorksInBluetoothLowEnergy.htm

How Encryption Works in Bluetooth low energy

Data encryption is used to prevent passive and active—man-in-the-middle (MITM) — eavesdropping attacks on a Bluetooth low energy link. Encryption is the means to make the data unintelligible to all but the Bluetooth master and slave devices forming a link. Eavesdropping attacks are directed on the over-the-air transmissions between the Bluetooth low energy devices, so data encryption is accomplished prior to transmission using a shared, secret key.

Briar is not available for iPhone. Only Android. This is a show stopper.